I've used ebuddy for messaging. It handles MSN, Facebook, Yahoo, AIM GTalk, Myspace, Hyves & ICQ.
Handcent for SMS. It has popups you can instant reply to. The notifications in the top bar aren't nearly as informative or polished as webOS, but the pop up capability makes quick responses a breeze.
Tethering? The Evo is a hotspot for up to 8 devices out of the box. 4g hotspot. Pretty sweet.
And don't think this is your ordinary Android OS. Sense adds quite a bit of polish on an otherwise clunky but functional OS. If the Evo were not Sensified, there wouldn't be near as much allure. Go play with the HTC Incredible at the Verizon store for a bit. That's the OS you're getting on the Evo. I wouldn't even entertain the Evo if it was stock Android. I absolutely hate email on it. One thing I love about webOS is email and messaging. It's just so convenient, even more so on the Pixi. IMAP folder support in Android sucks as bad as it does on BB. K9 helps, but it syncs horribly with the server and navigating through it is too tedious and not very intuitive. Sense helps a lot with email.
Not a fanboy of anything either. I manage our Sprint account and gladly recommend things based on our reps' needs. We have an assortment of Android, webOS and BB phones with two iPhone hold outs, and we give them $60/mo which is what we'd be paying for them on Sprint since they choose AT&T. As long as they check their Exchange mail, I could care less what they use.
And I don't know who made Dell's phones, if it's HTC or some other mfg, but the Smoke and Lightning make the Pre and Pixi look like kids' toys. I pray one of those comes to the CDMA side in some way, shape or form. I don't know why HTC has abandoned hard key phones, but if they make Dell's new ones, they better a) pitch those design concepts to Palm in hopes of a partnership or b) slap an HTC brand on them for Android. I'd take either with Sense in a heartbeat.